Extension-ladder.



J. A. JOHNSON. EXTENSION LADDER.

APPLICATION FILED JULY 27. 1906.

g5g q gg Patented Mar. 15, 1910.

UNTTE S AT JOSEPH AUSTIN JQHNSON, OF HAMPTON, NEW HAMPSHIRE.

EXTENSION-LADDER.

Application fi1ed July 27', 1906.

To aZZ whom it may concern:

Be it known that I, Josnri-r AUSTIN J 01-msoN, a citizen of the UnitedStates, residing at Hampton, in the county of Roeklngham and State of.New Hampshire, have in vented certain new and useful Improvements inExtension-Ladders, of which the following is a specification.

My invention relates to that class of extension ladders which consistsof two or more sections, (generally of two sections), one of which fitsloosely between the sides of the other and is readily slidable thereinso as to be quickly raised or lowered to extend the ladder.

The object of the invention is to provide such ladders with improvedmeans whereby the movable section may be easily and quickly raised andlowered, quickly and readily stopped and held atany desired point in theextension thereof, or permitted to be lowered into its bottom positionfor purposes of storage or transportation.

In order that others skilled in the art to which my invention mostnearly appertains may be enabled to make and use the same, I will nowproceed to describe the construc tion and operation thereof, inconnection with the accompanying drawing, in which Figure 1 is a partialsectional view on a plane cutting vertically through the ladder rounds,the hook and dog being in the positions assumed when the movable sectionis being raised. Fig. 2 is a similar View with the hook and dog in thepositions they assume when supporting the extensible or slidable sectionin its extended or partially extended position. Fig. 3 is a similar viewwith the hook and dog in the positions they assume when the beak of thehook rests upon a round of the stationary section, the dog being shownin dotted lines in the position it holds when passing a round of thestationary section. Fig; 41 is a similar view with the hook and dog inposition to per initthe extensible section to be moved downward in thestationary section without engaging the hook with the rounds of theladder. Fig. 5 is a face view in elevation of a hook and dog removedfrom the ladder. Like reference characters mark the same parts in all ofthe figures of the drawing.

Referring specifically to the drawing, 7, is the stationary section and,8 the slidable section of any ordinary extension ladder, the latter,being of proper dimensions to Specification of Letters Iatent.

Patentedlttar. 15, 191(1). Serial No. 328,100.

permit of its sliding up and down between the standards of the former,the sections 7, 8, having rounds of any preferred or ordinaryconstruction marked respectively 9, 10, 11, and 12. There are two hooks13, pivotally secured at their lower ends opposite to each other to theinner face of the two standards of the slidable section by screws orbolts 14., the points of such hooks being extended beyond their engagingends to form beaks 15, 15, which beaks are of the same lengths as thehooks themselves and have slightly curved or inclined ends 16. Thesehooks are so arranged that their centers of gravity, when the ladder isvertical, and more so when the ladder is inclined as in the position torest its upper end against a building, are inside of the vertical planespassing through their pivots, whereby the natural tendency of the beaksof the hooks is to press or rest upon the rounds of the section 7 (andfor the hooks to pass over said rounds) when the section 8 is moved onthe section 7. This action takes place automatically as the slidablesection is raised so that by slightly dropping this section when thehooks are above any round of section 7, the hooks will engage upon theround, as the round 10 in Fig. :2, and thus securely hold the section 8raised or extended. During the raising of the slidable section itnecessary that some provision be made to prevent the ends 16 of beaks 15from passing under the rounds of the stationary section. This isaccomplished by curving the shank of the hook so that during theextension of the ladder its edge 13 will bear with cam-like actionagainst the round-of the stationary section next below the one about tobe reached by the end 10 of the beak 15, whereby, as the ladder isextended, the parts are brought from the position shown in Fi 2 tosubstantially that shown in Fig. 1. If the shank of the hook werestraight it is obvious that the end 16 of the beak 15 would pass belowor behind the round of the stationary section and prevent the furtherupward movement of the slidable section. In this position of Fig. 1 itwill be observed that the straight main body, 15, of the beak is in thesame plane as the center of the curved cam-like surface 13 of the hookand which plane is coincident with or parallel to the inner surface ofthe standards of the slidable section which rests upon the rounds of themovable section. This plane in which the beak lies is outside of thevertical plane of the pivot 14 thus, as stated before, bringing thecenter of gravity of the hook and beak, outside of the vertical plane ofsaid pivot 1 1, even when the ladder is vertical, which is of importanceon account of the fact that it is very often convenient and very oftennecessary, especially with heavy ladders, to extend the slidable sectionwhen the ladder is in a vertical position.

In order that the hooks 13 may not engage the rounds of section 7 whenit is desued to lower sald sectlon 8, I provide balanced dogs or pawls17, 17 which are pivot ally secured on the inner sides of the hooks atnear the mid-length of said hooks, said pawls or dogs having extensions18, 18, beyond their pivots, of the same weight as the dogs themselvesso as to form, with the dogs, a balanced guard which will normally standin a balanced, substantially horizontal position.

When section 8 is held up by the hooks, as in Fig. 2, and it is desiredto lower it to its bottom position which would bring the hooks belowround 10, said section 8 is raised until the pawl reaches the positionof Fig. 3 when, as soon as the dog slips past, or above the round 10,(see dotted line in said figure), its extension 18 will drop to asubstantially horizontally balanced position as shown in dotted lines inFig. 1 so that the dog proper is in the track of the rounds of thestationary section 7 Now the section 8 may be lowered to any desiredextent, the dog being pressed upward, as it rides over the rounds ofsection 7, to the position shown in Fig. at and causing the hooks topass over the round below without engaging therewith. In the position ofFig. 4c, and while being pressed to that position by the rounds overwhich it is passing in the downward movement of the slidable section,the movement of the dog on its pivot is limited by a pin 19 projectingfrom the hook 18 against which the dog 17 impinges, the extension beingbent aside, as clearly shown in Fig. 5, so that it will clear the pin 19and the thickened portion of the hook.

The hooks 13 are prevented from falling back on their pawls out ofoperative position, by means of pins 20 projecting from the inner facesof the standards of the slidable section upon which said hooks will restwhen the ladder is moved from place to place, if tilted in the oppositedirection from that assumed when the ladder is set up against abuilding.

It will be observed that in order to operate as before described tolower the movable section, the distance from the point 21 of the hook tothe point of the dog when in the reverse position of Fig. 3, must beless than the distance between the rounds ofthe section 7, so that thedog may tilt on its pivot into the balanced or horizontal position andthen to the position of Fig. 4 to guard the point of the hook.

The length of the beak and hook combined being greater than the distancebetween adjacent rounds of the stationary section, it will be impossiblefor the hook at any time to fall forward between the rounds and as aconsequence, the point of the beak will always be in position to passover said rounds when the movable section is being raised, therebyavoiding the liability of accidentally obstructing the outward orlengthening adjustment.

\Vhat I claim as new is:

The combination with the movable section of an extension ladder, ofhooks pivotally mounted at their lower ends on the inner faces of thestandards of the sections, and provided with fiatbeaks, the terminals ofwhich are curved to provide fenders, the intermediate portion of thehooks being arranged to engage with an adjacent round to swing the hooksto permit the fenders to clear the next adjacent round,balanced dogspivotally connected with the shanks of the hooks intermediate of theirends and provided with offset extensions and arranged automatically toswing in the path of the hooks to prevent the latter from catching onthe rounds of the stationary section when the movable section islowered, and stops to limit the swinging movement of the dogs in twodirections.

In testimony whereof I aflix my signature in presence of two witnesses.

JOSEPH AUSTIN JOHNSON.

IVitnesses BENJIMIN J. Boo'rnn'orn, Ina S. JONES.

